A developing device is mounted in an electrophotographic image forming apparatus. Developer containing toner is stored inside the developing device. The developing device develops an electrostatic latent image formed on an image carrying member such as a photoconductor drum, by the toner contained in the developer. A toner image developed on the image carrying member is fixed to a print sheet by a fixing device. After the fixing, toner that was not fixed to the print sheet by the fixing device may remain on the image carrying member. With regard to this problem, there is known a waste toner collecting device for removing the toner remaining on the image carrying member and collecting the toner as waste toner.
The waste toner collecting device of this type includes a waste toner container for storing removed waste toner. Conventionally, there is known an image forming apparatus that can use, as a waste toner container, a toner replenishing container that had been used to replenish toner to the developing device and had become empty (see PTL 1). In this image forming apparatus, a configuration is made such that when the empty container is attached to the waste toner collecting device, a part of the empty container is deformed such that the deformed empty container cannot be attached to a replenishment attachment portion for the toner replenishing container. This prevents the empty container from being erroneously attached to the replenishment attachment portion, preventing waste toner from being erroneously used.